This invention relates in general to cushions and more particularly to cellular cushions used for seating.
Those who are confined to seating surfaces for sustained periods of time run the risk of developing decubitus ulcers, more commonly known as bed sores, along the skin area that is presented toward or against the seating surface. The problem is particularly acute where the bony prominences of the pelvic bone, that is the ischia, protrude toward the seating surface. Of course, decubitus ulcers are less likely to develop over a soft surface, such as a cushion, than over a relatively hard surface such as a bench or sling type wheelchair seat. Even so, conventional cushions, such as those formed from expanded polymers, leave much to be desired and do not adequately accommodate those who are confined in a seated posture for extended periods of time.
With the introduction of the cellular cushion, a vast improvement occurred in the capacity to seat immobile individuals for extended periods of time without the development of decubitus ulcers. These cushions, which are sold under the trademark ROHO, have a multitude of flexible air cells which project upwardly from a common base, yet are otherwise detached from one another. The interiors of the cells, however, are in communication with each other through the base, and as a consequence the interiors of all the cells exist at the same pressure, irrespective of how little or how much the individual cells are deflected. Of course, when a person sits upon such a cushion, the cells will deflect to conform to that individuals body contour. Some of the cells will deflect more than others, and the cells beneath the bony prominences will perhaps deflect most of all. Nevertheless, the restoring or supporting force exerted by the cells is distributed over essentially the entire skin area that is in contact with the cushion, and that force, when considered per unit of area, remains essentially uniform. In other words, the cushion exerts a uniform pressure over the supported region of the body, which is normally the buttocks.
Despite their capacity to reduce the incidence of decubitus ulcers, cellular cushions may leave the occupant of such cushions feeling somewhat unstable.
U.S. Pat Nos. 4,005,236, 4,541,136 and 4,698,864 of R. H. Graebe disclose cellular cushions that are suitable for seating purpose, and when so used will reduce the incidence of decubitus ulcers substantially.
The present invention resides in a cellular cushion having cells of varying heights arranged such that they produce a supporting surface more in conformance with the shape of the occupants buttocks, yet slightly abducts the thighs. As a consequence, the cushion provides improved stability, greater comfort, and lessens still further the risk of bed sores developing.